CAR String Format

The CAR string is a compact, immutable identifier encoding an agent's identity, capability domains, autonomy level, and version.

Canonical Format

{registry}.{organization}.{agentClass}:{domains}-L{level}@{version}[#extensions]

Components

Component	Description	Rules
registry	Hosting registry	Lowercase alphanumeric
organization	Registering org	Lowercase alphanumeric + hyphens
agentClass	Agent type name	Lowercase alphanumeric + hyphens
domains	Capability domain codes	Uppercase A–S, sorted alphabetically
level	Capability level	0–7
version	Spec version	Semver (major.minor.patch)
extensions	Optional extensions	Comma-separated shortcodes after #

Examples

a3i.vorion.banquet-advisor:FHC-L3@1.2.0
a3i.acme-corp.invoice-bot:ABF-L3@1.0.0
a3i.hospital-net.triage-agent:DHS-L4@2.0.0
a3i.vorion.classifier:DF-L2@1.0.0#cognigate

Validation Regex

const CAR_REGEX = /^([a-z0-9]+)\.([a-z0-9-]+)\.([a-z0-9-]+):([A-Z]+)-L([0-7])@(\d+\.\d+\.\d+)(?:#([a-z0-9,_-]+))?$/;

ABNF Grammar

car-string   = registry "." organization "." agent-class
               ":" domains "-L" level "@" version [ "#" extensions ]

registry     = 1*( ALPHA / DIGIT )
organization = 1*( ALPHA / DIGIT / "-" )
agent-class  = 1*( ALPHA / DIGIT / "-" )
domains      = 1*ALPHA                    ; uppercase A-S, sorted
level        = DIGIT                       ; 0-7
version      = 1*DIGIT "." 1*DIGIT "." 1*DIGIT
extensions   = shortcode *( "," shortcode )
shortcode    = 1*( ALPHA / DIGIT / "-" / "_" )

Design Decisions

Trust Tier is NOT in the CAR String

Unlike the legacy ACI format, the canonical CAR string does not include a trust tier. Trust is:

1. Dynamic — changes based on behavior, context, and time
2. Context-dependent — different in different deployments
3. Computed at runtime from:

Trust Score = (Certification × 0.3) + (Behavior History × 0.4) + (Context × 0.3)

The effective autonomy an agent receives is:

Effective Autonomy = MIN(CAR_Certification_Tier, Vorion_Runtime_Tier)

Domain Codes are Sorted Alphabetically

FHC → CHF (Communications, Finance, Hospitality sorted). This ensures the same set of domains always produces the same string.

Extensions are Optional

The #extensions suffix enables Layer 4 runtime governance without breaking backward compatibility.

Legacy Format (Deprecated)

The old ACI format included trust tier in the string:

{registry}.{organization}.{agentClass}:{domains}-L{level}-T{tier}@{version}

This format is still parsed for backward compatibility but should not be used for new registrations.

TypeScript Types

interface ParsedCAR {
  car: string;               // Original CAR string
  registry: string;
  organization: string;
  agentClass: string;
  domains: DomainCode[];     // Sorted array of domain codes
  domainBitmask: number;     // Bitmask encoding of domains
  level: CapabilityLevel;    // 0-7
  version: string;           // Semver
  extensions?: string[];     // Optional extension shortcodes
}